Return Value

An IQueryable<IGrouping<TKey, TElement>> in C# or IQueryable(Of IGrouping(Of TKey, TElement)) in Visual Basic where each IGrouping<TKey, TElement> contains a sequence of objects of type TElement and a key.

Type Parameters

TSource

The type of the elements of source.

TKey

The type of the key returned by the function represented in keySelector.

The GroupBy<TSource, TKey, TElement>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource, TElement>>, IEqualityComparer<TKey>) method generates a MethodCallExpression that represents calling GroupBy<TSource, TKey, TElement>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource, TElement>>, IEqualityComparer<TKey>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource, TKey, TElement>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource, TElement>>, IEqualityComparer<TKey>) depends on the implementation of the type of the source parameter. The expected behavior is that it groups the elements of source by a key value that is obtained by invoking keySelector on each element. Key values are compared by using comparer. The elementSelector parameter is invoked on each element to obtain a result element.